Prevalence of non-convulsive seizure and other electroencephalographic abnormalities in ED patients with altered mental status

Abstract

Four to ten percent of patients evaluated in emergency departments (ED) present with altered mental status (AMS). The prevalence of non-convulsive seizure (NCS) and other electroencephalographic (EEG) abnormalities in this population is unknown Objectives To identify the prevalence of NCS and other EEG abnormalities in ED patients with AMS. Methods A prospective observational study at two urban ED. Inclusion: patients ≥13 years old with AMS. Exclusion: An easily correctable cause of AMS (e.g. hypoglycemia). A 30-minute standard 21-electrode EEG was performed on each subject upon presentation. Outcome: prevalence of EEG abnormalities interpreted by a board-certified epileptologist. EEGs were later reviewed by two blinded epileptologists. Inter-rater agreement (IRA) of the blinded EEG interpretations is summarized with kappa. A multiple logistic regression model was constructed to identify variables that could predict the outcome. Results 259 patients were enrolled (median age: 60, 54% female). Overall, 202/259 of EEGs were interpreted as abnormal (78%, 95% confidence interval [CI], 73–83%). The most common abnormality was background slowing (58%, 95%CI, 52–68%) indicating underlying encephalopathy. NCS (including non-convulsive status epilepticus [NCSE]) was detected in 5% (95%CI, 3–8%) of patients. The regression analysis predicting EEG abnormality showed a highly significant effect of age (p<0.001, adjusted odds ratio 1.66 [95%CI, 1.36–2.02] per 10-year age increment). IRA for EEG interpretations was modest (kappa: 0.45, 95% CI, 0.36–0.54). Conclusions The prevalence of EEG abnormalities in ED patients with undifferentiated AMS is significant. ED physicians should consider EEG in the evaluation of patients with AMS and a high suspicion of NCS/NCSE.

Ictal and interictal EEG patterns in patients with nonconvulsive and subtle convulsive status epilepticus

“…In previous studies, NCSE was observed in 8% of comatose patients in an ICU [1], in 5% of all patients with altered mental status attending emergency departments [2], in 9.3% inpatients referred for EEG with clinical suspicion of NCSE [3], and in 9.8% of inpatient emergent EEGs [4]. The frequency in our study was lower compared to the above numbers as our denominator was all the inpatient EEGs.…”

Non-convulsive status epilepticus: a practical approach to diagnosis in confused older people

“…This contrasts with a study based in a US emergency department that found a prevalence of NCSE of 3% among a selected group of adults (median age 60 years, range 45–76, 259 EEGs performed) presenting with altered mental status (ranging from lethargy to coma) 8. A French study that looked at patients aged >60 (mean age 76, range 60–97, 44 EEGs performed) who had had an EEG to determine the cause of confusion of unknown origin (after initial investigations did not reveal the answer) found that 16% had EEG traces compatible with NCSE 9.…”

Effect of MicroEEG on Clinical Management and Outcomes of Emergency Department Patients With Altered Mental Status: A Randomized Controlled Trial

“…The 2-hour work-up period cutoff for T1 and T2 was selected based on the median time for enrollment to completion of EEG using microEEG in our previous study. 4 …”

“…3 The new microEEG also shortens the duration and amount of preparation needed to obtain an EEG without interfering with other ongoing diagnostic testing. 4 The wireless aspect allows real-time reporting of EEG results, which has the potential to affect clinical care.…”